The Computer History Museum in Mountain View, California
A great collection of old computers, well documented and photographed
The DigiBarn Computer Museum in Boulder Creek, California
PDF versions of Maximum PC magazine from December 2003 - Present
A great online museum for vintage computers
Excellent online resource for pre-1994 computers (w/ detailed pictures)
Erik S. Klein's vintage computer collection. Great information and pictures.
A great collection of old and hard to find documents from a huge range of manufacturers
An excellent resource for CPU information
A great resource for older motherboard and laptop documentation
A large and rather unruly collection of hardware documentation (French language site, documents in multiple languages)
A solid collection of laptop manuals old and new
A huge lot of vintage hardware diagrams, jumper settings, and more.